An ore pass is an inclined, vertical or near-vertical opening or passage for the transfer of ore or other material in underground mines using the force of gravity.
Ore passes may be of two general types, namely, full and flow-through. In both systems, the ore is dumped into the ore pass and eventually ends up at a loading point. Following this, the ore is typically transferred via a secondary transport method such as a railcar, conveyor, etc. In a full ore pass system, a certain level of ore is maintained in the ore pass at all times. Although there is an increased risk of hang-ups associated with this system, it greatly reduces ore pass degradation because there are fewer high energy impacts with ore pass walls. Keeping the ore pass full also allows for the stability and shape of the ore pass to be maintained. In a flow-through ore pass system, ore is dumped into the ore pass when available and flows down to the loading point. Hang-ups are less likely to occur in a flow-through system because the ore is allowed to flow most of the way down the pass without delay. Despite the prevention of hang-ups with the flow-through system, this system often results in degradation of the ore pass. As the material travels further along the pass, it gains momentum and the accumulation of impacts has the potential to cause structural damage to the ore pass.
Thus, ore passes are used to deliver ore or other material to a loading point which may be a chute box, bin, hopper, silo, etc. Unloading of ore from the chute box may be carried out using an underflow or side discharge opening or chute formed in the chute box. The chute may be used to transfer the ore or other material to a railcar system or other means by which the ore or other material may be transferred to the surface or elsewhere.
The chute of the chute box has a control gate that is typically opened and closed by an operator using a hydraulic control system. Several different types of control gates may be used such as press gates, undercut arc gates, guillotine gates, finger gates, or bar and chain gates.
Hazards associated with ore passes are a significant safety problem in underground mines. Injury and fatality data show that many injuries are related to pulling or freeing hang-ups in ore pass chutes and to mechanical failures of chutes, control gates, and ore pass walls.
In particular, current ore chute designs typically use a hydraulic accumulator (i.e., a pressure storage device) for storing energy to safely close the control gate in the event of an emergency or power failure. However, if the hydraulic accumulator is not monitored or maintained, the potential for failure and resulting damage or injury remains.
A need therefore exists for an improved ore chute system. Accordingly, a solution that addresses, at least in part, the above and other shortcomings is desired.